1. Field of the Invention
The present invention relates to a synchronizer for manual transmission and a method thereof, and more particularly to a simplified synchronizer for a manual transmission with an improved changing-speed feeling in forward and reverse changing-speed operations.
2. Description of Prior Art
In general, a manual transmission of an automobile changes power generated from an engine into proper driving force and outputs it in accordance with changes in driving states of the automobile, which provides an optimum driving capability.
As shown in FIGS. 7 and 8, the manual transmission comprises a plurality of levels of driving gears (first, second, third, fourth, fifth and backward) 50 assembled and idled at input shaft I, a synchronizer 51 disposed among the driving gears 50 for rotating along with the input shaft I to transmit/block power to the driving gears 50 in response to operation by shifting levers (not shown) and a plurality of driven gears 52 fixed at the output axis and meshed with the driving gears 50.
In order to manipulate the synchronizer 51 with the shifting levers, a plurality of shifting rails (R) are assembled with a plurality of shifting forks (P) fixed thereon. In order to transmit power conveyed by the differential gear (D) of an output axis (O) to wheels at both sides, a differential unit (DF) is coupled therewith.
The synchronizer 51 is constructed to synchronize the rotational speed of the input shaft I and the driving gears 50 with a braking torque by steps to smoothly change speeds. In order to simplify the structure of the synchronizer, a separate reverse synchronizer is not prepared. Instead, only a device is used for simply stopping the input shaft I and then for accomplishing the reverse changing speed.
As shown in FIG. 9, the aforementioned synchronizer is constructed with a clutch hub 54 coupled with the input shaft I for rotation and a plurality of key slots 53 formed at the periphery thereof, an synchro-key 56 inserted at the key slots 53 with its internal surface being supported by a synchronizing spring 55 to be loaded for extending outside, a clutch sleeve 58 coupled at the outer surface of the clutch hub 54 with a sleeve gear 57 assembled at the lower side thereof for enabling to slide toward the input shaft and to rotate with the synchro-key 56 being closely attached to the internal surface thereof, a synchronizer ring 61 positioned at the lateral surface of the clutch sleeve 58 with a first frictional surface 59 of a cone shape formed at the internal peripheral surface thereof for accomplishing synchronization by being pushed by the synchro-key 56 and a synchro-gear 60 for coupling the sleeve gear 57, and shifting gears 63 extensively formed at the driving gears 50 with a second frictional surface 62 to rub with the first frictional surface 59 by steps.
Particularly, a predetermined size of a protruder 64 and a groove 65 are formed at the position where the synchro-key 56 and the clutch sleeve 58 contact with each other for pushing the synchronizer ring 61 if less than a predetermined level of force is applied, or for letting the clutch sleeve 58 climb over the synchro-key 56 if more than a predetermined level of force is applied.
In addition, in order to perform the reverse changing-speed operations, there are provided a brake ring 68 disposed at one side of the clutch sleeve 58 for being pushed by the shynchro-key 56 and has a third frictional surface 66 formed at its internal peripheral surface and a brake gear 67 for meshing with the sleeve gear 57, a ring-shaped reverse cone part 70 fixedly on mounted a transmission case C and formed with a fourth frictional surface 69 for being rubbed with the third frictional surface 66 by steps when the brake ring 68 is pushed.
A wave spring 71 is assembled between the transmission case and the brake ring 68 for pushing the brake ring 68 to be apart from the reverse cone part 70 after completion of the reverse changing-speed operation.
At this time, when the clutch sleeve 58 is moved to a direction R, a reverse changing-speed lever 72 and a reverse shifting gear 73 shown in FIG. 8 move to mesh with a reverse gear tooth 74 formed at the first/second clutch sleeve 58', referred to as symbol RG in FIG. 7, and a reverse driving gear 75 fixed at the input shaft I. Then, the reverse changing-speed operation is completed.
Now, the operations of the synchronizer will be described. If the shifting lever is manipulated, for instance, to carry out the shifting operation to the fifth level, the clutch sleeve 58 is moved to the right in the drawing.
If the clutch sleeve 58 is moved to the right, the synchro-key 56 tightly attached to the internal peripheral surface of the clutch hub 54 at a predetermined level of force moves to push the synchronizer ring 61. At this time, the first and second frictional surfaces 59, 62 are rubbed to start synchronizing the rotational speed of the clutch sleeve 58 and the driving gear 50.
If the rotational speed of the clutch sleeve 58 and the driving gear 50 gets synchronized, the clutch sleeve 58 climbs over the protruder 64 of the synchro-key 56 to be meshed with the shychro-gear 60 of the synchronizer ring 61 and then passes through it to be meshed with the shifting gear 63 of the driving gear 50. When the clutch sleeve 58 and the shifting gear 63 of the driving gears 50 are meshed, a changing-speed operation is completed.
At this time, procedures of the reverse changing-speed operation will be described. If the shifting lever is put to the reverse driving position, the clutch sleeve 58 moves to the direction R as indicated in the drawing (to the left in the drawing).
If the clutch sleeve 58 moves to the direction R, the synchro-key 56 pushes the brake ring 68 to get rubbed the third and fourth frictional surfaces 66, 69 respectively formed at the brake ring 68 and at the reverse cone part 70, thereby reducing the rotational speed of the clutch sleeve 58, that is, the input shaft I.
If the rotational speed of the clutch sleeve 58 reduces, the clutch sleeve 58 meshes with the brake gear 67 of the brake ring 68 to press down the wave spring 71.
At this time, while the reverse changing-speed lever 72 shown in FIG. 8 moves along with the clutch sleeve 58, the reverse gear 73 interlocked at the reverse changing-speed lever 72 moves to be meshed between the reverse gear tooth 74 of the first/second clutch sleeve 58' and the reverse driving gear 75 as shown in FIG. 10.
If the reverse changing-speed operation is completed as described above, the force that pushes the brake ring 68 is exhausted to get the brake ring 68 apart from the reverse cone part 70 due to elasticity of the wave spring 71, thereby being able to reversely drive.
The synchronizer of the manual transmission described above comprises, in order to synchronize the driving gear and the clutch sleeve, the shynchro-key which slides to the axis from the clutch hub, the clutch sleeve which moves the synchro-key at a predetermined level of force to synchronize the synchronizer ring and the driving gear and is meshed with the shifting gear of the driving gear at more than a predetermined level of force, and the synchronizer spring which supports the synchro-key. However, there is a problem in the conventional synchronizer in that the structure thereof is complicated and the assembling capability of the synchro-key and others are poor, thereby increasing manufacturing cost and lowering assembling efficiency.
In addition, in order for the clutch sleeve to push the synchronizer ring at a predetermined level of force to be meshed with the shifting gear of the driving gear, the protruder and groove should be provided between the shynchro-key and the clutch sleeve. Therefore, there is another problem in the conventional synchronizer in that, when the clutch sleeve climbs over the protruder and groove during changing-speed operations, the changing-speed feeling declines.
Particularly, there is another problem in the conventional synchronizer in that, when the clutch sleeve and the brake ring are operated during reverse changing-speed procedure, the force, larger than elasticity of the wave spring, should be applied, thereby needing larger manipulating strength to cause inconveniences in performing changing-speed operations.
Therefore, it is an object of the present invention to solve the aforementioned problems and to provide a synchronizer for power transmission and a method thereof to simplify the structure of the synchronizer of the manual transmission, to improve assembling efficiency of the synchronizer and to make a progress in changing-speed feeling at the time of a reverse changing-speed operation.
In order to accomplish the aforementioned objects, there is provided a synchronizer of a manual transmission constructed with a clutch hub rotated along with an input shaft, a clutch sleeve assembled for performing rotation with the clutch hub to move toward the input shaft and a synchronizer ring formed for meshing with the clutch sleeve when the clutch sleeve moves to be synchronized with driving gears by friction, the synchronizer comprising:
A synchro-lever formed with an upper portion thereof closely attached to a groove of the clutch sleeve and a lower portion thereof positioned at a lateral surface of the clutch hub when its portion is accommodated into a key slot of the clutch hub, to thereby perform a synchronizing operation with the driving gear by pushing the synchronizer ring positioned at one side thereof when tilted clockwise or counter-clockwise by being caught on the clutch hub in moving toward the input shaft; and
an accommodating part formed as a space within the clutch hub, the synchronizer ring and the driving gear for letting the synchro-lever rotate at a predetermined angle to cause a portion thereof to contact with the synchronizer ring.
In addition, there is provided a synchronizing method for the manual transmission, in which a clutch sleeve performing rotations along with an input shaft moves toward the input shaft to synchronize a shynchronizer ring with driving gears, and then the clutch sleeve meshes with the driving gears and the synchronizer ring to convey power, the method comprising a step where a synchro-lever is tilted clockwise or counter-clockwise to push the synchronizer ring closely positioned at the synchro-lever in order to synchronize the driving gears mounted at one side thereof when the clutch sleeve moves to the left or the right.